Do most people do ok with just the methylcobalmin or do some people need the adenosylcobalamin? Would the OAT guide this choice?

Yes, some people do need adenosylcobalamin as well. But it depends on the results of a person’s Organic Acid Test. I typically just recommend starting with methylcobalmin. If someone is very deficient in adenosylcobalamin, they can try taking adenosylcobalamin later. But methylcobalmin is usually enough for most people.